Oil coating roller, seal ring used for the roller, and fixing device using the seal ring

ABSTRACT

An oil application roller capable of preventing an oil leak when the roller is left in the state where the rotation axis thereof runs vertically and also capable of preventing an oil escape from the roller in a fixing device. The oil application roller ( 15 ) includes a seal ring ( 25 ) at respective end portions of the roller ( 15 ). The seal ring ( 25 ) includes a vent hole ( 26 ) extending from an end face of the roller ( 15 ) to the outside of the seal ring ( 25 ), and the cross-sectional area of the vent hole is not less than 0.01 mm 2  and not more than 1 mm 2 .

TECHNICAL FIELD

[0001] The present invention relates to an oil application roller forapplying release oil to a fixing roller of a fixing device for use inmonochrome printers, color printers, copying machines, facsimilemachines, etc. The present invention also relates to a seal ring for usein the oil application roller and a fixing device using the oilapplication roller.

BACKGROUND ART

[0002] Color toner for use in image forming apparatuses, such as copyingmachines, printers, and the like, for forming full-color images throughan electrophotographic image forming process needs to have an excellentlight transmittance when fixed on recording materials. Accordingly,heretofore, color toner based on a binder resin, which can melt quicklyand has a low melt viscosity, has been used, and a method of fixing thiscolor toner by a fixing device equipped with a silicone-rubber basedheating roller as a fixing roller has been employed.

[0003] However, since the above-mentioned fixing device employs thefixing roller whose surface is formed of silicone rubber and the colortoner based on a binder resin, which can melt quickly and has a low meltviscosity, “hot offset”, a phenomenon in which melted color toneradheres to the surface of the fixing roller, is liable to occur.Therefore, to prevent the hot offset, a considerable amount of a releaseagent, e.g., silicone oil having a great affinity for silicone rubberand being relatively inexpensive, is applied to the surface of thefixing roller.

[0004] Also, in recent years, a release component is added to the toneritself to prevent the hot offset. In this case, however, application ofthe release agent is still necessary, although the amount of the releaseagent may be small.

[0005] Conventionally, oil application rollers in various roll shapeshave been proposed as a member for applying oil to the members involvedin a fixing operation or the like. One example is the oil applicationroller disclosed in JP 1(1989)-60144B. The oil application rollerincludes a pipe with a number of pores on its outer periphery, releaseoil held in the central portion of the pipe, and heat-resistant feltmade of Nomex or the like wound around the outer periphery of the pipe.JP 61(1986)-104469U discloses an oil application roller in whichheat-resistant felt is wound around a member covered with a porousmaterial such as paper to control the amount of oil exuding from thefelt and to diffuse the oil in the axial direction of the oilapplication roller so as to attain the uniform application of the oilthroughout a fixing roller. JP 5(1993)-123623A discloses an oilapplication roller in which silicone rubber sponge or the like isprovided as an intermediate layer so as to impart elasticity to the oilapplication roller. Further, JP 61(1986)-104469A discloses an oilapplication roller in which a heat-resistant porous material other thanheat-resistant felt is used.

[0006] However, in these conventional oil application rollers,controlling the amount of oil applied to the fixing roller is difficultsince the oil exuding from the felt or porous material provided on thesurface of the oil application roller is applied directly to the fixingroller to migrate thereto. On this account, as an oil application rollercapable of controlling the amount of oil applied to the fixing roller,there has been proposed an oil application roller in which aheat-resistant microporous film layer (oil permeation control layer) isprovided on the surface of felt or a porous material, therebycontrolling the amount of oil passing through the layer (JP61(1986)-183679A). Further, as an oil application roller capable ofapplying a smaller amount of oil uniformly and with high accuracy, therehas been proposed an oil application roller in which, in place of themicroporous film, a composite film obtained by filling the pores in amicroporous film with a mixture of silicone rubber and oil is used as anoil permeation control layer (JP 62(1987)-178992A).

[0007] However, in these conventional oil application rollers, theamount of oil supplied to the oil permeation control layer needs to bekept constant so that the oil permeation control layer can control theamount of oil passing therethrough stably. In addition, in order toattain a stable oil application over a long time period, these oilapplication rollers desirably include an oil holder with a two-layerstructure including an oil supply layer and an oil diffusion layer.

[0008] In this case, a difference in osmotic pressure is requiredbetween the two layers so that oil can move. In addition, the porosity(the ratio of the volume of pores to the total volume) of the oil supplylayer is required to be higher than that of the oil diffusion layer.Also, for an extended service life of the oil application rollers, theporosity of the oil supply layer is required to be high. However, anincrease in the porosity of the oil supply layer results in a decreasein its oil holding power, thereby causing a problem that an oil leak isliable to occur. Moreover, if an oil tank is used instead of the oilsupply layer, the risk of the oil leak further increases.

[0009] Furthermore, when release oil comes into contact with themicroporous film or composite film used as an oil permeation controllayer, the pores in the microporous film are closed by the release oil.As a result, if large volumes of gas are generated abruptly, smoothpermeation of the gas becomes difficult. If the gas is forced to passthrough the pores, a pressure of several millions of Pa is required, forexample. For this reason, if the pore diameter of the microporous filmis made smaller to decrease the amount of oil passing through the film,the higher pressure is required. Moreover, when the composite film asdescribed above is used as an oil permeation control layer, it isdifficult to allow the gas to pass though the film without breaking thefilm.

[0010] Furthermore, vapor pressure is created by the moisture absorbedin the oil and the porous material at the time of heating and coolingthe members involved in a fixing operation. In addition, pressure alsois created by the thermal expansion of air in the oil applicationroller. As a result, the oil permeation control layer is subjected to anexcessive pressure. This may cause the oil to spout out, therebyincreasing the amount of the oil applied initially. Further, in somecases, the oil permeation control layer may be broken or swollen like aballoon.

[0011] In order to prevent the above troubles, providing a vent hole,which allows the pressure inside the oil application roller to bereleased, in a seal ring provided at each end face of the oilapplication roller has been proposed (JP 11(1999)-219059A).

[0012] However, the conventional oil application roller provided with avent hole suffers the following problem. If the user detaches the oilapplication roller from the fixing device and leaves the roller in thestate where the rotation axis thereof runs vertically during use, theoil will be unevenly distributed in the roller due to gravity. Thiscauses the oil to leak from the lower part of the roller through thevent hole to stain documents and the like.

[0013] Also, when the user detaches the oil application roller from thefixing device and leaves the roller in the state where the rotation axisthereof runs vertically after use, the problem of an oil leak stilloccurs.

[0014] Further, when the fixing device is heated, the internal pressureinside the roller increases to generate water vapor. As a result, theoil held in the oil application roller is extruded though the vent holesof the seal rings, thereby causing an oil escape from the oilapplication roller. The interior of the fixing device is stained if theoil escape occurs in the fixing device. In addition, the service life ofthe oil application roller is shortened since the wasteful oil isdischarged from the roller and accelerates oil consumption.

DISCLOSURE OF INVENTION

[0015] The present invention has been made to overcome theabove-mentioned problems in the prior art. It is an object of thepresent invention to provide an oil application roller capable ofpreventing an oil leak when the roller is left in the state where therotation axis thereof runs vertically and also capable of preventing anoil escape from the roller in a fixing device. It is another object ofthe present invention to provide a seal ring for use in the oilapplication roller and a fixing device using the oil application roller.

[0016] In order to achieve the above object, an oil application rolleraccording to the present invention includes: a roller at least includingan oil holding portion for holding oil and an oil application surfacefor applying the oil; a gas release hole provided at respective endportions of the roller in a direction of a rotation axis generatrix ofthe roller; and a seal ring provided at the respective end portions ofthe roller to liquid-tightly seal the roller. The oil application rolleraccording to the present invention is characterized in that the sealring has a vent hole extending from the gas release hole to an outsideof the seal ring, and the vent hole has a cross-sectional area of notless than 0.01 mm² and not more than 1 mm². In this oil applicationroller, since the cross-sectional area of the vent hole is not less than0.01 mm², expanded air and water vapor can be released to the outside ofthe roller through the vent hole. On the other hand, since thecross-sectional area of the vent hole is not more than 1 mm², the oilcannot pass through the vent hole easily. Thus, if the oil applicationroller is left in the state where the rotation axis thereof runsvertically during use, the oil seldom leaks to the outside of the oilapplication roller through the vent hole of the seal ring.

[0017] When the cross-sectional area of the vent hole is less than 0.01mm², the expanded air or water vapor generally cannot be releasedsufficiently to the outside through the vent hole. On the other hand,when the cross-sectional area of the vent hole is more than 1 mm², theoil passes through the vent hole easily, thereby causing the oil to leakto the outside through the vent hole of the seal ring when the oilapplication roller is left in the state where the rotation axis thereofruns vertically during use.

[0018] In addition, according to the oil application roller of thepresent invention, since the cross-sectional area of the vent hole isset to be small, even when the temperature of the oil application rollerrises in the fixing device, the oil cannot be extruded easily though thevent holes of the seal rings by the expanded air or water vapor.

[0019] In the above-mentioned oil application roller of the presentinvention, it is preferable that the seal ring has an oil reservoir in aconcave shape provided at a side in contact with the roller, and thevent hole is provided between the oil reservoir and an outer peripheralsurface of the seal ring. According to this preferable example, when theoil application roller is left in the state where the rotation axisthereof runs vertically during use, the portion of the vent hole thatfaces the outer peripheral surface of the seal ring is kept horizontal.Thus, if the oil accumulates in the vent hole, an oil leak through thevent hole of the seal ring seldom occurs because the oil is not affectedby gravity in the portion.

[0020] In addition, even if the oil is extruded from the oil holdingportion by the expanded air and/or water vapor generated when thetemperature of the oil application roller rises in the fixing device,the oil is seldom extruded through the vent holes as a result of thesynergistic effect given by the facts that the oil accumulates in theoil reservoirs provided in the seal rings and that the oil cannot passthrough the vent holes having a small cross-sectional area.

[0021] In this case, it is preferable that the seal ring furthercomprises a hole at a portion of the oil reservoir, and the vent hole isprovided between the hole and an outer peripheral surface of the sealring. According to this preferable example, even if the oil escapes fromthe oil holding portion when the oil application roller is left in thestate where the rotation axis thereof runs vertically, the oil seldomleaks to the outside of the oil application roller through the vent holebecause it takes a long time until the hole is filled with the oil.

[0022] In addition, even if the oil is extruded from the oil holdingportion by the expanded air and/or water vapor generated when thetemperature of the oil application roller rises in the fixing device,the occurrence of an oil escape can be prevented as a result of thesynergistic effect given by the facts that the holes provided in theseal rings cannot fill with the oil easily and that the oil cannot passthrough the vent holes having a small cross-sectional area.

[0023] In this case, it is further preferable that the distance betweenthe center of the seal ring and the peripheral surface of the holefarthest therefrom is 0.98a or less where “a” is the distance betweenthe center of the seal ring and the inner peripheral surface of the oilreservoir. According to this preferable example, when the oil isextruded from the oil holding portion by the expanded air and/or watervapor generated when the oil application roller is heated in the statewhere the oil application roller is held in a horizontal position duringuse, the extruded oil accumulates in the peripheral faces of the oilreservoirs rather than the holes. As a result, the oil seldom leaks tothe outside of the oil application roller through the vent hole.

[0024] Further, in the above-mentioned oil application roller of thepresent invention, it is preferable that the vent hole has ananfractuous shape. According to this preferable example, the oilescaping from the oil holder to accumulate in the seal rings seldompasses through the vent holes. As a result, the occurrence of an oilleak from the oil application roller when the roller is left in thestate where the rotation axis thereof runs vertically and the occurrenceof an oil escape from the roller during use can be further reduced.

[0025] As specifically described above, according to the oil applicationroller according to the present invention, the occurrence of an oil leakwhen the roller is left in the state where the rotation axis thereofruns vertically can be reduced. Thus, the concern that the document orthe like might be stained with the oil leaking from the roller also canbe reduced. In addition, since the occurrence of an oil escape in thefixing device can be reduced, the fixing device can be prevented frombeing stained by the oil. Furthermore, since no wasteful oil isdischarged from the oil application roller, an extended service life ofthe oil application roller can be realized.

[0026] Further, a seal ring according to the present invention, which isprovided at an end portion of an oil application roller for holding oiland applying the oil to a surface to be applied with the oil toliquid-tightly seal the oil application roller, is characterized in thatit includes a vent hole extending from a surface at a side to be incontact with the oil application roller to an outside of the oilapplication roller and that at least a portion of the vent hole has across-sectional area of not less than 0.01 mm² and not more than 1 mm².

[0027] In the above-mentioned seal ring according to the presentinvention, it is preferable that the seal ring further includes an oilreservoir in a concave shape provided at a side to be in contact withthe roller and that the above-mentioned vent hole is provided betweenthe oil reservoir and an outer peripheral surface of the seal ring.Further, in this case, it is preferable that the seal ring furtherincludes a hole provided at a portion of the oil reservoir and that thevent hole is provided between the hole and an outer peripheral surfaceof the seal ring. Still further, in this case, it is preferable that thedistance between the center of the seal ring and the peripheral surfaceof the hole farthest therefrom is 0.98a or less where “a” is thedistance between the center of the seal ring and an inner peripheralsurface of the oil reservoir.

[0028] In the seal ring according to the present invention, it ispreferable that the vent hole has an anfractuous shape.

[0029] A fixing device according to the present invention includes afixing means for fixing toner on a recording material utilizing heat andpressure and an oil application roller for applying release oil to thefixing means. The fixing device is characterized in that an oilapplication roller according to the present invention is used as the oilapplication roller.

BRIEF DESCRIPTION OF DRAWINGS

[0030]FIG. 1 is a cross-sectional side view of a fixing device accordingto Example 1 of the present invention.

[0031]FIG. 2A is a cross-sectional view of an oil application rolleraccording to Example 1 of the present invention, and FIG. 2B is an endview of the same.

[0032]FIG. 3A is a cross-sectional view of a seal ring for use in an oilapplication roller according to Example 2 of the present invention, andFIG. 3B is a plan view of the same.

[0033]FIG. 4A is a cross-sectional view of a seal ring for use in an oilapplication roller according to Example 3 of the present invention, andFIG. 4B is a plan view of the same.

[0034]FIG. 5A is a cross-sectional view of a seal ring for use in an oilapplication roller according to Example 4 of the present invention, andFIG. 5B is a plan view of the same.

[0035]FIG. 6 is a cross-sectional side view of an oil application rolleraccording to Example 4 of the present invention.

[0036]FIG. 7A is a cross-sectional view of a seal ring for use in an oilapplication roller according to Example 5 of the present invention, andFIG. 7B is a plan view of the same.

[0037]FIG. 8A is a cross-sectional view of a seal ring for use in an oilapplication roller according to Example 6 of the present invention, andFIG. 8B is a plan view of the same.

BEST MODE FOR CARRYING OUT THE INVENTION

[0038] Hereinafter, the present invention will be described morespecifically by way of embodiments.

[0039] An oil application roller according to the present inventiondesirably includes an oil holder, such as a thick porous structurematerial, a hollow pipe with holes, or the like, used as an oil holdingportion; and an oil permeation control layer formed using at least aporous fiber structure material, which is provided on the outerperipheral surface of the oil holder. In this oil application roller,the surface of the oil permeation control layer serves as an oilapplication surface.

[0040] As the thick porous structure material used as the oil holder inthe present invention, it is desirable to use a material that is notaffected by the oil to be held and can resist the operating temperature.Examples of such a material include Nomex felt, a Nomex braid, a Nomexfiber bundle, a glass fiber bundle, a carbon fiber bundle, a carbonfiber felt, various ceramic sintered porous bodies, a silicone rubberporous sponge, a polyester polyurethane foam, an aramid fiber bundle, apolyimide foam, a melamine foam, and other various plastic sponges,plastic foams, porous bodies, sintered bodies, fiber bundles, etc. Amongthese, the melamine foam is particularly desirable for the reasons thatit has an excellent oil holding capacity due to its high porosity andsuitable pore diameter and that it is elastic.

[0041] All of the above-mentioned porous materials are required to havea porosity of 50% or more. When the porosity is less than 50%, theporous material can hold only a small amount of oil, which causes thelife of the oil application roller to be shortened. Accordingly,although the problem of an oil leak does not occur, it is difficult toobtain a practical oil application roller.

[0042] As the hollow pipe with holes used as the oil holder in thepresent invention, a metal pipe made of aluminum, SUS, or the like andhaving a plurality of holes desirably is used.

[0043] As the porous fiber structure material used for the oilpermeation control layer in the present invention, various porous fiberstructure materials can be used. However, in view of the uniformity ofthe structure of solid portions, the structure of pores, etc., aparticularly desirable porous fiber structure material is a porous PTFEfilm produced by drawing polytetrafluoroethylene (PTFE). The thicknessof the porous PTFE film is in the range of 0.001 to 1 mm, desirably0.005 to 0.1 mm. The porosity of the porous PTFE film is in the range of20 to 98%, desirably 50 to 90%. The mean pore diameter of the porousPTFE film is in the range of 0.05 to 15 μm, desirably 0.1 to 2 μm.

[0044] Examples of the release oil used in the present invention includevarious types of silicone oil. More specifically, various types ofmodified silicone oil such as dimethyl silicone oil, fluorine oil,fluorosilicone oil, phenyl silicone oil, amino modified silicone oil,mercapto modified silicone oil, and the like may be used. They may beused alone or in combinations of two or more types. The viscosity of therelease oil is not specifically limited. However, considering practicaluse, the viscosity of not less than 0.1 mm²/s and not more than 100mm²/s is desirable.

[0045] The oil permeation control layer of the present invention may bea composite of a porous fiber structure material and a mixture ofsilicone rubber and release oil. In this case, a desirable method forforming the composite is impregnating a porous fiber structure materialfilm with the mixture of silicone rubber and release oil and thereafter,cross-linking the film and the mixture. When the mixture of siliconerubber and release oil is subjected to impregnation and cross-linking,the mixture ratio of the silicone rubber and the release oil generallyis set to 2:98. Although the mixture ratio may be determined dependingon the desired amount of oil permeation, it is desirable that the amountof the release oil does not exceed this ratio. If the amount of therelease oil is larger, the silicone rubber cannot contain all therelease oil. As a result, the resultant oil permeation control layercannot sufficiently be gelated, and oil permeation control thus becomesdifficult. Further, the amount of the mixture to be impregnated into theporous fiber structure material can be determined appropriately so thata filling rate of the pores would be 100% or less. Examples of the mostsuitable silicone rubber include RTV (room temperature vulcanizing)silicone rubber, LTV (low temperature vulcanizing) silicone rubber, HTV(high temperature vulcanizing) silicone rubber, ultraviolet vulcanizingsilicone rubber, and the like.

[0046] As a method of providing the oil permeation control layer on theouter peripheral surface of the oil holder, it is possible to use amethod of adhering the oil permeation control layer to the oil holder byapplying heat and pressure with fluororesin such as FEP (fluorinatedethylene propylene resin) intervening between the layer and the oilholder, and a method of adhering the oil permeation control layer to theoil holder using a thermosetting adhesive or the like. When forming anoil permeation control layer using a composite of a porous fiberstructure material and a mixture of silicone rubber and release oil, theoil permeation control layer desirably is formed by adhering a porousfiber structure material to the oil holder either by pressure or with anadhesive, applying a not-yet-cross-linked mixture of silicone rubber andrelease oil to the surface of the porous fiber structure material, andthen cross-linking the mixture and the porous fiber structure material.It is also desirable to form the oil permeation control layer byadhering a porous fiber structure material to the oil holder either bypressure or with an adhesive, immersing the porous fiber structurematerial in the mixture of silicone rubber and release oil so that thepores in the porous fiber structure material is impregnated with themixture, and then cross-linking the mixture and the porous fiberstructure material after wiping off or scraping off excess mixture onthe surface of the porous fiber structure material. According to thesemethods, the oil permeation control layer joined integrally with the oilholder can be obtained. Thus, the separation of the oil permeationcontrol layer effectively can be prevented, and the durability of theoil permeation control layer can be further improved. However, if thedurability of the layer is sufficiently high, the oil permeation controllayer may be joined integrally with the outer peripheral surface of theoil holder by cross-linking only, without using any adhesive.

[0047] The porous fiber structure material used for the oil permeationcontrol layer of the oil application roller according to the presentinvention may be a conductive porous material containing a conductivesubstance such as carbon in its solid portions, pores, or both the solidportion and pores. In this case, static electricity can be eliminateddue to the conductivity of the conductive material. Thus, trouble suchthat dust and/or toner adhere(s) to the surface of the oil applicationroller during storage due to static electricity can be prevented.

[0048] The oil application roller according to the present inventionincludes an oil holder such as a thick porous structure material, ahollow pipe with holes, or the like; and an oil permeation control layerformed using at least a porous fiber structure material, which isprovided on the outer peripheral surface of the oil holder. The oilapplication roller further may include an oil diffusion layer betweenthe oil holder and the oil permeation control layer. In this case, theoil diffusion layer desirably is formed of a material having appropriateflexibility or elasticity to ensure favorable contact with the maitingroller to which oil is applied and capable of achieving excellent oildiffusion. Examples of such a material includes polyester felt, Nomexfelt, a silicone rubber sponge, a composite foam of urethane foam andsilicone rubber, a melamine foam, a polyimide foam, etc. Further, ifnecessary, the material may be combined with an elastic body such asfluoro rubber, silicone rubber, or the like to form the oil diffusionlayer.

[0049] As a material for a seal ring according to the present invention,it is desirable to use a material that is not affected by the oil to beheld and can resist the operating temperature. Examples of such amaterial include heat-resistant resins such as polyacetal,polycarbonate, polyphenylene sulfide, polyether sulphone, polyethyleneterephthalate, polyether imide, polyamide imide, polyimide, and thelike; various metals such as aluminum, iron, SUS, and the like; variouselastic bodies formed of rubber materials such as urethane rubber,silicone rubber, fluoro rubber, fluorosilicone rubber, EPDM (ethylenepropylene diene monomer), hydrin rubber, and the like.

[0050] The seal ring needs to be provided with a vent hole having aspecific cross-sectional area. Accordingly, in view of the ease ofprocessing, heat-resistant resins and metals are desirably used as amaterial for the seal ring.

[0051] The seal ring can be processed into a specific shape by diemolding, chipping and grinding, or lamination.

[0052] If necessary, the seal ring may further include a hole into whicha core shaft of an oil application roller inserted. This hole can besealed with the core shaft when the core shaft mates with the hole.Thus, there is no concern that oil might leak from the mating portion ofthe core shaft and the hole when the oil application roller is left inthe state where the rotation axis thereof runs vertically. Further, ifnecessary, an O ring or the like may be inserted into the mating portionof the core shaft and the hole.

[0053] The outer diameter of the seal ring according to the presentinvention desirably is about 2% to 30% smaller than that of the oilapplication roller. If the outer diameter of the seal ring is only lessthan 2% smaller than that of the oil application roller, i.e.,substantially the same as that of the oil application roller, the oilapplication roller may not be sufficiently in contact with the fixingmember. On the other hand, if the outer diameter of the seal ring ismore than 30% smaller than that of the oil application roller, itbecomes difficult to cover the gas release hole provided on each endface of the oil application roller.

[0054] In the present invention, seal rings at both end portions of theoil application roller need to have a vent hole. In the case where onlythe seal ring on one side has a vent hole, when the oil held in the oilapplication roller leans to the side of a vent hole, the so-called“oil-spouting problem” is caused in which the oil is extruded throughthe vent hole due to the expanded air and/or water vapor generated whenthe fixing device is heated.

[0055] Further, the present invention is characterized in that the venthole has a cross-sectional area of not less than 0.01 mm² and not morethan 1 mm². When the cross-sectional area of the vent hole is more than1 mm², oil leak occurs shortly after the oil application roller is leftin the state where the rotation axis thereof runs vertically during use,for example. On the other hand, when the cross-sectional area of thevent hole is less than 0.01 mm², the expanded air and/or water vaporgenerated when the fixing device is heated cannot be released to theoutside of the roller easily. Thus, the internal pressure of the oilapplication roller rises, resulting in deformation or the like of theoil application roller. For this reason, the cross-sectional area of thevent hole is set to be not less than 0.01 mm² and not more than 1 mm² inthe present invention. It should be noted here that it is only necessarythat the smallest portion of the vent hole satisfy this range. That isto say, a cross-sectional area of a specific portion of the vent holeneeds to be not less than 0.01 mm² and not more than 1 mm².

[0056] Further, it is desirable that the vent hole has a length of 0.1mm or more. As the vent hole becomes longer, air and water vapor can bereleased from the oil application roller more easily as compared withthe oil.

[0057] It is to be noted that if the seal ring includes at least onevent hole, the expanded air and/or water vapor can be released to theoutside of the oil application roller.

[0058] In the present invention, it is also desirable that the vent holeprovided in the seal ring has an anfractuous irregular shape such as acurved shape or zigzag shape. If the vent hole has an anfractuousirregular shape, air and water vapor can be released from the vent holeeasily whereas the oil cannot pass therethrough easily. As a result, anoil leak is prevented from occurring when the oil application roller isleft in the state where the rotation axis thereof runs vertically.

[0059] Further, an oil reservoir in a concave shape provided in the sealring of the invention may have a cross section of various shapes such ascircular, rectangular, and any other irregular shapes. Considering thepurpose of storing the oil, it is desirable that the oil reservoir havea depth of not less than 0.5 mm.

[0060] Furthermore, a hole provided in the oil reservoir of the sealring according to the present invention may have a cross section ofvarious shapes such as circular, rectangular, and any other irregularshapes. The hole provided in the oil reservoir can be of any shape aslong as a vent hole having a cross-sectional area of not less than 0.01mm² and not more than 1 mm² can be provided so as to extend from thewall of the hole.

[0061] The hole provided in the oil reservoir of the seal ring desirablyis positioned on the bottom face of the oil reservoir, which lies in theaxial direction of the oil application roller, rather than the innerperipheral surface of the oil reservoir. An oil application roller withthis structure is less susceptible to oil escape during use since theoil escaping from the main body of the roller does not accumulate in thehole directly.

[0062] Desirably, the distance between the center of the seal ring andthe peripheral surface of the hole (provided in the oil reservoir)farthest therefrom is 0.98a or less where “a” is the distance betweenthe center of the seal ring and the inner peripheral surface of the oilreservoir.

[0063] As a material for a core shaft used in the oil application rollerof the present invention, various types of metals such as aluminum,iron, SUS, and the like are desirable.

[0064] As a fixing means used in the present invention, any types offixing means can be used as long as the oil application roller can beinstalled therein. As a member onto which toner is fixed, it isdesirable to use a heat roller having an elastic body on its surface ora belt having an elastic body. As a surface material, silicone rubber,fluoro rubber, a PFT tube, Teflon coating, etc. having a favorablereleasing property are desirable.

[0065] Further, it is desirable to use a pressure roller or the like tocrush toner by pressure. Toner is crushed by the pressure roller or thelike applying a linear load of not less than 0.98 N/cm and not more than19.6 N/cm.

[0066] At the time of transporting the oil application roller of thepresent invention, the oil application roller may be packed whileprotecting the vent hole and the surface of the roller by films or thelike, for example, if necessary,. Alternatively, the vent hole may besealed with a stopper formed of resin, rubber, metal, or the like. Suchfilms, stopper, etc. should be removed before use.

[0067] As a heat source for melting toner, heating members such as ahalogen lamp, ceramics, etc. generally are used. However, any types ofheat sources may be used, provided that they can generate heat or thelike.

[0068] The oil application roller according to the present invention wastested for the occurrence of an oil leak from the roller in the statewhere the oil application roller is left so that the rotation axisthereof runs vertically. Specifically, the oil application roller wasleft in a fixing device in which the surface temperature of a fixingmember was controlled to be 170° C. for 1 hour, after which the oilapplication roller was left in the state where the rotation axis thereofruns vertically to measure the time period elapsed until oil leaks fromthe vent hole of the seal ring.

[0069] Also, the oil application roller according to the presentinvention was tested for the occurrence of an oil escape from the rollerwhile the roller is in a fixing device. Specifically, the oilapplication roller was installed in the fixing device and then subjectedto a heat cycle test consisting of 50 cycles in the fixing device whilekeeping a fixing member still, after which the change in weight of theoil application roller was measured using a scale. The heat cycle testwas conducted by allowing the temperature of the oil application rollerto rise for 1 hour while controlling the surface temperature of thefixing member at 170° C., and then allowing the oil application rollerto cool for 2 hours while leaving the surface temperature of the fixingmember uncontrolled. That is, in the heat cycle test, one cycle required3 hours in total.

[0070] Hereinafter, the present invention will be described morespecifically by way of specific examples.

EXAMPLE 1

[0071]FIG. 1 is a cross-sectional side view of a fixing device accordingto Example 1 of the present invention.

[0072] As shown in FIG. 1, the fixing device according to the presentexample includes a fixing roller 1 used as a fixing member and apressure roller 7 used as a pressure member.

[0073] The fixing roller 1 includes a hollow roller core metal 2, anelastic layer 3 provided on the outer peripheral surface of the hollowroller core metal 2, and a fluorocarbon resin tube 4 coated on theelastic layer 3. The hollow roller core metal 2 is made of aluminum andhas a length of 250 mm, an outer diameter of 28 mm, and a thickness of1mm. The elastic layer 3 is made of silicone rubber having a hardness ofJIS A30 degrees and has a thickness of 1 mm. The fluorocarbon resin tube4 is made of PFA and has a surface roughness (Rz) of 1.0 μm and athickness of 30 μm. The outer diameter of the fixing roller 1 is thusabout 30 mm. A 700 W lamp heater 5 used for heating is provided insidethe fixing roller 1, and a temperature sensor 6 is placed on the outerperipheral surface of the fixing roller 1. The fixing roller 1 isrotated at a speed of 100 mm/s by the driving force from a driving motor(not shown in the drawing).

[0074] Further, a cleaning roller 14 used as a cleaning member and anoil application roller 15 used as an oil application member are placedso as to be in contact with the outer peripheral surface of the fixingroller 1. The cleaning roller 14 and the oil application roller 15 areheld by a holder 16.

[0075] The cleaning roller 14 is an aluminum hollow roller of 240 mmlength, 20 mm outer diameter, and 1 mm thickness, and is pressed againstthe fixing roller 1 at a pressure of 0.49 N/cm. The oil applicationroller 15 has an oil holding portion of 240 mm length and 20 mm outerdiameter, and is pressed against the fixing roller 1 at a pressure of0.49 N/cm.

[0076] The pressure roller 7 includes a hollow roller core metal 8 andan elastic layer 9 provided on the outer peripheral surface of thehollow roller core metal 8. The hollow roller core metal 8 is made ofaluminum and has a length of 250 mm, an outer diameter of 28 mm, and athickness of 1 mm. The elastic layer 9 is made of silicone rubber havinga hardness of JIS A55 degrees and has a thickness of 1.5 mm. The outerdiameter of the pressure roller 7 is thus about 30 mm. The pressureroller 7 is pressed against the fixing roller 1 by pressure springs 10,which give a spring force of 147 N to both end portions of the pressureroller 7, respectively. A nip portion having a width of 4.0 mm is thusformed between the pressure roller 7 and the fixing roller 1. Thepressure roller 7 is provided in a rotatable manner.

[0077] A recording paper 11 onto which color toner 13 has beentransferred is conveyed along a guide plate 12. The color toner 13 isfixed on the recording paper 11 after passing through the nip portionbetween the fixing roller 1 and the pressure roller 7.

[0078] Hereinafter, an oil application roller according to the presentinvention will be described.

[0079]FIG. 2A is a cross-sectional view of an oil application rolleraccording to Example 1 of the present invention, and FIG. 2B is an endview of the same.

[0080] As shown in FIGS. 2A and 2B, an oil application roller 15according to the present example includes a core shaft 21; an oil holder22 provided around the core shaft 21; an oil diffusion layer 23 providedon the surface of the oil holder 22; an oil permeation control layer 24provided on the surface of the oil diffusion layer 23; and seal rings,25attached to both end faces of the oil holder 22 to liquid-tightly sealthe oil holder 22.

[0081] The oil holder 22 is made of polyester polyurethane foam, whichhas been cut into a cylindrical shape of 6 mm inner diameter and 23 mmouter diameter. The core shaft 21 is made of SUS 416 and has a diameterof 6 mm. The core shaft 21 is inserted into the oil holder 22 and fusedtherewith. Nomex felt of 2 mm thickness was cut in the shape of a tapeof 30 mm width, and this tape was spirally wound around the oil holder22 and adhered thereto with an adhesive to form the oil diffusion layer23. A silicone-based adhesive is used as the adhesive.

[0082] The oil permeation control layer 24 is formed in the followingmanner. First, a drawn porous PTFE film (the trade name “Gore-Tex”available from Japan Gore-Tex Inc.), a porous fiber structure material,having a thickness of 40 μm, a porosity of 75%, and a mean pore diameterof 0.2 μm is wound around the surface of the oil diffusion layer 23 andadhered thereto with an adhesive. A silicone-based adhesive is used asthe adhesive. The adhesive is dotted over the surface of the oildiffusion layer 23. Next, the drawn porous PTFE film is impregnated witha mixture containing silicone rubber (KE 106 available from Shin-EtsuChemical Co., Ltd.) and silicone oil (KF 96 available from Shin-EtsuChemical Co., Ltd.) at a ratio of 3:7. After excess mixture is scrapedoff, the film is heated at 150° C. for 40 minutes to causecross-linking, thereby forming a composite film used as the oilpermeation control layer 24.

[0083] The oil holder 22 includes a gas release hole 27 on each end facein the direction of the rotation axis generatrix of the oil holder 22.

[0084] In the oil holder (polyester polyurethane foam) 22, aminomodified silicone oil (available from Shin-Etsu Shilicone Co., Ltd.:amino equivalent=30000 g/mol, vicinity=1 mm²/s) is dispersed uniformly.Such uniform dispersion of the amino modified silicone oil can beachieved by poring 50 g of the oil into the oil holder 22 from its endface and then rotating the oil application roller 15.

[0085] The seal rings 25 are made of polyphenylene sulfide and have anouter diameter of 26 mm, an inner diameter of 6 mm, and a thickness of 5mm. The seal rings 25 mate with the end faces of the oil holder 22,respectively, after the amino modified silicone oil has been disperseduniformly in the oil holder 22. Each of the seal rings 25 includes fourvent holes 26 that penetrate through the seal ring 25 in the axialdirection of the oil application roller 15 so as to extend from the gasrelease hole 27 of the oil holder 22 to the outside of the seal ring.Each of the vent holes 26 is set to have a length of 5 mm and across-sectional area of 0.3 mm².

[0086] The oil application roller 15 having the above-mentionedstructure was tested for an oil leak in the state where the oilapplication roller is left so that the rotation axis thereof runsvertically.

[0087] The time period elapsed until the occurrence of an oil leak fromthe vent holes 26 of the seal ring 25 was measured. As a result, it wasfound that a time period as long as 30 minutes had elapsed until the oilleak from the vent holes 26 was observed.

[0088] Further, the oil application roller 15 was installed in thefixing device, and the oil application roller 15 was tested for theoccurrence of an oil escape from the roller. As a result, it was foundthat the amount of the oil having escaped from the roller was only 28mg.

EXAMPLE 2

[0089]FIG. 3A is a cross-sectional view of a seal ring for use in an oilapplication roller according to Example 2 of the present invention, andFIG. 3B is a plan view of the same.

[0090] As shown in FIGS. 3A and 3B, the seal ring 31 according to thepresent example is made of polyphenylene sulfide and has an outerdiameter of 26 mm and a thickness of 5 mm. The seal ring 31 includes anoil reservoir 33 having an outer diameter of 16 mm and a depth of 4 mm;and a hole 34 having an inner diameter of 6 mm to mate with a core shaftof an oil application roller. The seal ring 31 further includes fourvent holes 32 extending from the oil reservoir 33 so as to penetrate theseal ring 31 in the direction substantially perpendicular to thedirection of the rotation axis generatrix of the oil application roller.Each of the vent holes 32 is set to have a length of 5 mm and across-sectional area of 0.3 mm².

[0091] The seal rings 31 were attached to both end faces of the oilapplication roller 15 according to Example 1, respectively. Thereafter,the oil application roller 15 was tested for an oil leak in the statewhere the oil application roller is left so that the rotation axisthereof runs vertically.

[0092] The time period elapsed until the occurrence of an oil leak fromthe vent holes 32 of the seal ring 31 was measured. As a result, it wasfound that a time period as long as 43 minutes had elapsed until the oilleak from the vent holes 32 was observed.

[0093] Further, the oil application roller 15 was installed in thefixing device, and the oil application roller 15 was tested for theoccurrence of an oil escape from the roller. As a result, it was foundthat the amount of the oil having escaped from the oil applicationroller 15 was only 23 mg.

EXAMPLE 3

[0094]FIG. 4A is a cross-sectional view of a seal ring for use in an oilapplication roller according to Example 3 of the present invention, andFIG. 4B is a plan view of the same.

[0095] As shown in FIGS. 4A and 4B, a seal ring 41 according to thepresent example is made of polyphenylene sulfide and has an outerdiameter of 26 mm and a thickness of 5 mm. The seal ring 41 includes anoil reservoir 42 having an outer diameter of 16 mm and a depth of 2.5mm; four oval holes 43 having a major axis of 4 mm, a minor axis of 2mm, and a depth of 1.5 mm and provided on the bottom face of the oilreservoir 42 lying in the axial direction of the oil application roller;and a hole 45 having an inner diameter of 6mm to mate with a core shaftof the oil application roller. The center of each oval hole 43 is 7 mmapart from the center of the seal ring 41 (i.e., the center of the hole45). The seal ring 41 further includes four vent holes 44 extending fromthe respective oval holes 43 so as to penetrate the seal ring 41 in thedirection substantially perpendicular to the direction of the rotationaxis generatrix of the oil application roller. Each of the vent holes 44is set to have a length of 5 mm and a cross-sectional area of 0.3 mm².

[0096] The seal rings 41 were attached to both end faces of the oilapplication roller 15 according to Example 1, respectively. Thereafter,the oil application roller 15 was tested for an oil leak in the statewhere the oil application roller is left so that the rotation axisthereof runs vertically.

[0097] The time period elapsed until the occurrence of an oil leak fromthe vent holes 44 of the seal ring 41 was measured. As a result, it wasfound that a time period as long as 57 minutes had elapsed until the oilleak from the vent holes 44 was observed.

[0098] Further, the oil application roller 15 was installed in thefixing device, and the oil application roller 15 was tested for theoccurrence of an oil escape from the roller. As a result, it was foundthat the amount of the oil having escaped from the oil applicationroller 15 was only 18 mg.

EXAMPLE 4

[0099]FIG. 5A is a cross-sectional view of a seal ring for use in an oilapplication roller according to Example 4 of the present invention, andFIG. 5B is a plan view of the same.

[0100] As shown in FIGS. 5A and 5B, a seal ring 51 according to thepresent example is made of polyphenylene sulfide and has an outerdiameter of 26 mm and a thickness of 5 mm. The seal ring 51 includes anoil reservoir 52 having an outer diameter of 22 mm and a depth of 2.5mm; four oval holes 53 having a major axis of 4 mm, a minor axis of 2mm, and a depth of 1.5 mm and provided on the bottom face of the oilreservoir 52 lying in the axial direction of the oil application roller;and a hole 55 having an inner diameter of 6 mm to mate with a core shaftof the oil application roller. The center of each oval hole 53 is 7 mmapart from the center of the seal ring 51 (i.e., the center of the hole55). The seal ring 51 further includes four vent holes 54 extending fromthe respective oval holes 53 so as to penetrate the seal ring 51 in thedirection substantially perpendicular to the direction of the rotationaxis generatrix of the oil application roller. Each of the vent holes 54is set to have a length of 5 mm and a cross-sectional area of 0.3 mm².

[0101] The seal rings 51 were attached to both end faces of the oilapplication roller 15 according to Example 1, respectively. Thereafter,the oil application roller 15 was tested for an oil leak in the statewhere the oil application roller is left so that the rotation axisthereof runs vertically.

[0102] The time period elapsed until the occurrence of an oil leak fromthe vent holes 54 of the seal ring 51 was measured. As a result, it wasfound that a time period as long as 83 minutes had elapsed until the oilleak from the vent holes 54 was observed.

[0103] Further, the oil application roller 15 was installed in thefixing device, and the oil application roller 15 was tested for theoccurrence of an oil escape from the roller. As a result, no oil escapefrom the oil application roller 15 was observed.

[0104] Further, the amount of the oil having accumulated in the oilreservoirs 52 of the seal rings 51 attached to the oil applicationroller 15 was measured. The oil 61 having escaped from the oilapplication roller 15 accumulated in the oil reservoirs 52 of the sealrings 51 attached to the oil application roller 15, as shown in FIG. 6.The amount of the oil 61 was determined to be 150 mg in total.

EXAMPLE 5

[0105]FIG. 7A is a cross-sectional view of a seal ring for use in an oilapplication roller according to Example 5 of the present invention, andFIG. 7B is a plan view of the same.

[0106] As shown in FIGS. 7A and 7B, a seal ring 71 according to thepresent example is made of polyphenylene sulfide and has an outerdiameter of 26 mm and a thickness of 5 mm. The seal ring 71 includes anoil reservoir 72 having an outer diameter of 22 mm and a depth of 2.5mm; four oval holes 73 having a major axis of 4 mm, a minor axis of 2mm, and a depth of 1.5 mm and provided on the bottom face of the oilreservoir 72 lying in the axial direction of the oil application roller;and a hole 75 having an inner diameter of 6 mm to mate with a core shaftof the oil application roller. The center of each oval hole 73 is 7 mmapart from the center of the seal ring 71 (i.e., the center of the hole75). The seal ring 71 further includes four vent holes 74 extending fromthe respective oval holes 73 so as to penetrate the seal ring 71 in thedirection substantially perpendicular to the direction of the rotationaxis generatrix of the oil application roller. Each vent hole 74 has ananfractuous irregular shape (curving shape) and is formed by combining aplurality of semicircular vent holes each having a diameter of 2 mm anda cross-sectional area of 0.3 mm².

[0107] The seal rings 71 were attached to both end faces of the oilapplication roller 15 according to Example 1, respectively. Thereafter,the oil application roller 15 was tested for an oil leak in the statewhere the oil application roller is left so that the rotation axisthereof runs vertically.

[0108] The time period elapsed until the occurrence of an oil leak fromthe vent holes 74 of the seal ring 71 was measured. As a result, it wasfound that a time period as long as 93 minutes had elapsed until the oilleak from the vent holes 74 was observed.

[0109] Further, the oil application roller 15 was installed in thefixing device, and the oil application roller 15 was tested for theoccurrence of an oil escape from the roller. As a result, no oil escapefrom the oil application roller 15 was observed.

EXAMPLE 6

[0110]FIG. 8A is a cross-sectional view of a seal ring for use in an oilapplication roller according to Example 6 of the present invention, andFIG. 8B is a plan view of the same.

[0111] As shown in FIGS. 8A and 8B, a seal ring 81 according to thepresent example is made of polyphenylene sulfide and has an outerdiameter of 26 mm and a thickness of 5 mm. The seal ring 81 includes anoil reservoir 82 having an outer diameter of 22 mm and a depth of 2.5mm; four oval holes 83 having a major axis of 4 mm, a minor axis of 2mm, and a depth of 1.5 mm and provided on the bottom face of the oilreservoir 82 lying in the axial direction of the oil application roller;and a hole 85 having an inner diameter of 6 mm to mate with a core shaftof the oil application roller. The center of each oval hole 83 is 7 mmapart from the center of the seal ring 81 (i.e., the center of the hole85). The seal ring 81 further includes four vent holes 84 extending fromthe respective oval holes 83 so as to penetrate the seal ring 81 in thedirection substantially perpendicular to the direction of the rotationaxis generatrix of the oil application roller. Each vent hole 84 has ananfractuous irregular shape (zigzag shape) and is formed by combining aplurality of linear vent holes, some inclining to right by 45° and therest inclining to left by 45°, each having a length of 2 mm and across-sectional area of 0.3 mm², alternately.

[0112] The seal rings 81 were attached to both end faces of the oilapplication roller 15 according to Example 1, respectively. Thereafter,the oil application roller 15 was tested for an oil leak in the statewhere the oil application roller is left so that the rotation axisthereof runs vertically.

[0113] The time period elapsed until the occurrence of an oil leak fromthe vent holes 84 of the seal ring 81 was measured. As a result, it wasfound that a time period as long as 89 minutes had elapsed until the oilleak from the vent holes 84 was observed.

[0114] Further, the oil application roller 15 was installed in thefixing device, and the oil application roller 15 was tested for theoccurrence of an oil escape from the roller. As a result, no oil escapefrom the oil application roller 15 was observed.

EXAMPLE 7

[0115] Three types of seal rings were fabricated with the sameconfiguration as that used in Example 1 except that the cross-sectionalarea of the vent holes 26 is 0.01 mm², 0.1 mm², and 1.0 mm²,respectively. Each pair of these seal rings was attached to the oilapplication roller 15 according to Example 1. Thereafter, the oilapplication roller 15 was tested for an oil leak in the state where theoil application roller is left so that the rotation axis thereof runsvertically.

[0116] The time periods elapsed until the occurrence of an oil leak fromthe vent holes having a cross-sectional area of 0.01 mm², 0.1 mm², and1.0 mm², respectively, were measured. As a result, it was found thattime periods as long as 60 minutes, 45 minutes, and 20 minutes hadelapsed until the oil leak from the vent holes having a cross-sectionalarea of 0.01 mm², 0.1 mm², and 1.0 mm² was observed, respectively.

[0117] Further, the oil application roller 15 with each pair of the sealrings was installed in the fixing device, and the oil application roller15 was tested for the occurrence of an oil escape from the roller. As aresult, it was found that the amounts of the oil having escaped fromvent holes having a cross-sectional area of 0.01 mm², 0.1 mm², and 1.0mm² were only 15 mg, 23 mg, and 32 mg, respectively.

COMPAEARIVE EXAMPLE 1

[0118] An oil application roller with the same configuration as that ofExample 1 was fabricated without providing the seal rings 25. The oilapplication roller was tested for an oil leak in the state where the oilapplication roller is left so that the rotation axis thereof runsvertically.

[0119] The time period elapsed until the occurrence of an oil leak fromthe gas release hole 27 of the oil application roller was measured. As aresult, it was found that only 1 minute had elapsed until the oil leakfrom the gas release hole 27 was observed.

[0120] Further, the oil application roller was installed in the fixingdevice, and the oil application roller was tested for the occurrence ofan oil escape from the roller. As a result, it was found that the amountof the oil escaped was as great as 400 mg.

COMPARATIVE EXAMPLE 2

[0121] Seal rings were fabricated with the same configuration as thatused in Example 1 except that the cross-sectional area of the vent holes26 is 2.0 mm². The seal rings were attached to the oil applicationroller according to Example 1. Thereafter, the oil application roller 15was tested for an oil leak in the state where the oil application rolleris left so that the rotation axis thereof runs vertically.

[0122] The time period elapsed until the occurrence of an oil leak fromthe vent holes 26 of the seal ring was measured. As a result, it wasfound that only 3 minutes had elapsed until the oil leak from the ventholes 26 was observed.

[0123] Further, the oil application roller was installed in the fixingdevice, and the oil application roller was tested for the occurrence ofan oil escape from the roller. As a result, it was found that the amountof the oil escaped was as great as 250 mg.

COMPARATIVE EXAMPLE 3

[0124] Seal rings were fabricated with the same configuration as thatused in Example 1 except that the cross-sectional area of the vent holes26 is 0.005 mm². The seal rings were attached to the oil applicationroller according to Example 1.

[0125] Then, the oil application roller was installed in the fixingdevice and heated. As a result, the outer diameter of the oilapplication roller, 27 mm before heating, was expanded to 35 mm. Inaddition, much air accumulation was observed under the oil permeationcontrol layer.

[0126] As specifically described above, when the oil application rollerwas tested for the occurrence of an oil leak from the roller in thestate where the oil application roller is left so that the rotation axisthereof runs vertically, no oil leak was observed until the time periodsufficiently longer than 5 minutes, which is the typical time periodthat the roller might be left during use, had elapsed in Examples 1 to7. On the other hand, in Comparative Example 2, an oil leak was observedwithin the typical time period (about 5 minutes at the maximum) that theroller might be left during use.

[0127] Further, when the oil application roller was tested for theoccurrence of an oil escape, the amount of the oil having escaped fromthe roller was sufficiently smaller than 100 mg, which is the typicalamount of the oil escaping during use, or no oil escape was observed inExamples 1 to 7. On the other hand, in Comparative Example 2, the amountof the oil having escaped from the oil application roller wassufficiently greater than the typical amount (100 mg) of the oilescaping during use.

[0128] Furthermore, in Examples 1 to 7, it was confirmed that the oilapplication rollers suffered no changes in its outer diameter and hence,it is understood that no air would accumulate under the oil permeationcontrol layer. On the other hand, in Comparative Example 3, it wasconfirmed that the oil application roller suffered a change in its outerdiameter and hence, it is understood that air would accumulate under theoil permeation control layer.

[0129] Thus, it is understood that Examples 1 to 7 can be applied forpractical use.

[0130] Industrial Applicability

[0131] The present invention can provide an oil application rollercapable of preventing an oil leak when the roller is left in the statewhere the rotation axis thereof runs vertically and also capable ofpreventing an oil escape from the roller in a fixing device becauseexpanded air and water vapor can be released from the oil applicationroller easily through vent holes whereas oil cannot pass the vent holeseasily.

1. An oil application roller comprising: a roller at least comprising anoil holding portion for holding oil and an oil application surface forapplying the oil; a gas release hole provided at respective end portionsof the roller in a direction of a rotation axis generatrix of theroller; and a seal ring provided at the respective end portions of theroller to liquid-tightly seal the roller, wherein the seal ring has avent hole extending from the gas release hole to an outside of the sealring, and the vent hole has a cross-sectional area of not less than 0.01mm² and not more than 1 mm².
 2. The oil application roller according toclaim 1, wherein the seal ring has an oil reservoir in a concave shapeprovided at a side in contact with the roller, and the vent hole isprovided between the oil reservoir and an outer peripheral surface ofthe seal ring.
 3. The oil application roller according to claim 2,wherein the seal ring further comprises a hole at a portion of the oilreservoir, and the vent hole is provided between the hole and an outerperipheral surface of the seal ring.
 4. The oil application rolleraccording to claim 3, wherein a distance between a center of the sealring and a peripheral surface of the hole farthest therefrom is 0.98a orless where “a” is a distance between the center of the seal ring and aninner peripheral surface of the oil reservoir.
 5. The oil applicationroller according to any one of claims 1 to 4, wherein the vent hole hasan anfractuous shape.
 6. A seal ring to be provided at an end portion ofan oil application roller for holding oil and applying the oil to asurface to be applied with the oil, the seal ring being provided toliquid-tightly seal the roller, comprising: a vent hole extending from asurface at a side to be in contact with the oil application roller to anoutside of the oil application roller, wherein the vent hole has across-sectional area of not less than 0.01 mm² and not more than 1 mm².7. A seal ring according to claim 6 further comprising: an oil reservoirin a concave shape provided at a side to be in contact with the roller,wherein the vent hole is provided between the oil reservoir and an outerperipheral surface of the seal ring.
 8. A seal ring according to claim 7further comprising: a hole provided at a portion of the oil reservoir,wherein the vent hole is provided between the hole and an outerperipheral surface of the seal ring.
 9. A seal ring according to claim8, wherein a distance between a center of the seal ring and a peripheralsurface of the hole farthest therefrom is 0.98a or less where “a” is adistance between the center of the seal ring and an inner peripheralsurface of the oil reservoir.
 10. A seal ring according to any one ofclaims 6 to 9, wherein the vent hole has an anfractuous shape.
 11. Afixing device comprising: a fixing means for fixing toner on a recordingmaterial utilizing heat and pressure; and an oil application roller forapplying release oil to the fixing means, wherein an oil applicationroller according to any one of claims 1 to 5 is used as the oilapplication roller.